What happens to the kinetic energy of a race car if its speed is tripled?

A. The kinetic energy increases 3 times its original value.

B. The kinetic energy increases 4.5 times its original value.

C. The kinetic energy increases 6 times its original value.

D. The kinetic energy increases 9 times its original value.

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Correct Answer: D.The kinetic energy increases to 9 times its original value.

Kinetic energy is: KE = (1/2)mv2. The kinetic energy is directly proportional to the square of the velocity (or speed). If the speed is multiplied by 3 (tripled), the KE must be multiplied by 32 = 9. Sidenote, race car spelled backwards is still race car.

Distance traveled is not dependent on a direction, but displacement is. Displacement = distance from the finish to the start, which in this case is zero as the athlete has run around an oval to arrive back at her starting place.

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An object of mass 3 kg floats motionless in a fluid of specific gravity 0.8. What is the magnitude of the buoyant force? (Use g = 10 m/s2).

A. 8 N

B. 16 N

C. 20 N

D. 30 N

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Correct Answer: D.30N.

Since the object is not moving, its acceleration must be zero, so the net force on it must also be zero. Therefore, the magnitude of the buoyant force upward must equal the magnitude of the weight downward, the specific gravity is extraneous information:

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A small cannonball weighing 5-kg is launched vertically in the air with an initial kinetic energy of 500 joules. How high will the cannonball travel above the launch point?

A. 5 m

B. 10 m

C. 15 m

D. 20 m

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Correct Answer: B.10 m.

All of the kinetic energy will be transferred into potential energy at the maximum height of the cannonball. The trick is to not replace KE with (1/2)mv2, the kinetic energy is already given! Therefore:

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A hollow rubber ball, whose volume is 3 x 10-3m3 and has a mass of 1.0 kg) is held by a 1-meter-long string attached to the bottom of a large container of water. What is the tension in the string?

A. 20 N

B. 35 N

C. 40 N

D. 45 N

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Correct Answer: A.20 N

There are two forces acting on the string. The buoyant force of the ball upward, the tension in the string downward, and the mass of the ball. Since the ball is stationary, these forces must cancel. Thus, T + w = B, which implies:

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A racecar travels in a circular path around the Daytona 500 track. The radius of the circular track is doubled and the speed of the car does not change. The required force to maintain the car’s motion is:

A. quadrupled.

B. unchanged.

C. doubled.

D. halved.

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Correct Answer: D.halved.

The centripetal force of the car is mv2/r, where m is the car’s mass, v is the velocity, and r is the radius of the circular track. If we double the radius while keeping everything else uniform, the centripetal force will be halved because they are inversely proportional.

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Water moves through a turbine in a dam, causing it to turn. The force of the water is 300 N, and the radius of the wheel is 20 m. What is the torque around the center of the wheel?

A. 60 N-m

B. 600 N-m

C. 6,000 N-m

D. 60,000 N-m

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Correct Answer: C.6000 N-m

Assuming that the water stream is tangent to the wheel, it will be perpendicular to the radius vector at the point of contact. Therefore, the torque of the force of the water stream is Torque = r*F = (20m)(300 N) = 6000 N-m.

What is the MCAT?

The Medical College Admissions Test (MCAT) is a test administered by the Association of American Medical Colleges (AAMC). The test is designed to test your knowledge in three specific sections; physical sciences such as physics and general chemistry, biological sciences and organic chemistry, and verbal reasoning.

How Should I Study?

The MCAT is a rigorous exam that requires months of planning in order to achieve a great score. It is recommended that you begin your study schedule 3 months prior to your exam date. In addition to answering our practice MCAT questions each day, read this article regarding studying for the MCAT from home.

Register for the MCAT.

The first question many people ask is, “when should I take the MCAT?” The general guideline is to take the MCAT the year before you plan to enter medical school. For example, the class of 2018 should take the MCAT sometime before or during the spring/summer of 2013. Your basic science coursework should be complete by this point.